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Defined Contribution Plan, Employee Contribution Percentage Received 2-for-1 Employer Match

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Defined Contribution Plan, Employer Discretionary Contribution Percentage of Earnings

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Defined Contribution Plan, Employer Matching Contribution for Every Pound on the First One Percent of Employee Contributions

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Pension and Other Postretirement Benefits Disclosure [Line Items]

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Private Equity Partnership Future Liquidation Term

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The average effective interest rate during the reporting period.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

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Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

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Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

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Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

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- Definition

Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

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Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

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Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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Ultimate trend rate for health care cost for defined benefit postretirement plan.

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Year ultimate health care cost trend rate is expected to be reached, in CCYY format.

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Amount of cost for defined contribution plan.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Description of nature and type of retirement benefits.

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Amount of cash outflow for pension benefit. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. Excludes other postretirement benefit.

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Employee Benefit Plans - Additional Information (Detail)		12 Months Ended
	Jan. 02, 2020 USD ($)	Dec. 31, 2019 GBP (£) Rate	Dec. 31, 2019 USD ($) Rate	Dec. 31, 2018 USD ($) Rate	Dec. 31, 2017 USD ($)
Pension and Other Postretirement Benefits Disclosure
Health Care Cost Trend Rate Assumed for Next Fiscal Year \| Rate			6.50%	7.00%
Ultimate Health Care Cost Trend Rate \| Rate			5.00%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate		2024	2024
Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation			$ 500,000
Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation			(500,000)
Future Amortization of Actuarial Gain (Loss)			19,800,000
Future Amortization of Prior Service Cost (Credit)			200,000
Pension Plan \| UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Plan Amendments			0	$ 0	$ 7,600,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid			$ 146,300,000	82,200,000
Average Remaining Life Expectancy of Plan Participants		26 years	26 years
Retirement Benefits, Description		We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2019	We had no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2019
Pension Plan \| UNITED STATES \| Group Annuity Contact
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Benefit Obligation, Benefits Paid			$ (59,500,000)
Pension Plan \| UNITED STATES \| Group Annuity Contact \| Subsequent Event
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Benefit Obligation, Benefits Paid	$ (44,000,000.0)
Pension Plan \| UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Plan Amendments			0	(300,000)
Defined Benefit Plan, Benefit Obligation, Benefits Paid			$ 4,800,000	7,300,000
Average Remaining Life Expectancy of Plan Participants		32 years	32 years
Payment for Pension Benefits			$ 0
Other Postretirement Benefit Plans
Pension and Other Postretirement Benefits Disclosure
Plan Amendments			0	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid			11,200,000	11,100,000
Investment Level 3 Transfers Into			0	0
Investment Level 3 Transfers Out of			$ 0	$ 0
Interest Rate During Period		4.74%	4.74%	4.73%
Other Postretirement Benefit Plans \| UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay \| Rate		5.00%	5.00%
Employer Discretionary Contribution Percentage of earnings \| Rate		4.50%	4.50%
Cost Recognized			$ 77,300,000	$ 72,700,000	78,400,000
Other Postretirement Benefit Plans \| UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Matching Contribution Percent of Employees' Gross Pay		5.00%	5.00%
Employer Discretionary Contribution Percentage of earnings		6.00%	6.00%
Employer Matching Contribution for Every Pound on the First One Percent of Employee Contributions \| £		£ 2
Employee Contribution Percentage Received 2-for-1 Employer Match		1.00%	1.00%
Cost Recognized			$ 4,400,000	$ 4,200,000	$ 4,200,000
Equity Securities \| Pension Plan \| UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			36.00%
Fixed Maturity Securities \| Pension Plan \| UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			40.00%
Interest Rate Contract \| Pension Plan \| UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			35.00%
Alternative Investments \| Pension Plan \| UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			24.00%
Diversified Growth Assets \| Pension Plan \| UNITED KINGDOM
Pension and Other Postretirement Benefits Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			65.00%
Minimum \| Private Equity Funds of Funds \| Pension Plan \| UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term		5 years	5 years
Maximum \| Private Equity Funds of Funds \| Pension Plan \| UNITED STATES
Pension and Other Postretirement Benefits Disclosure
Private Equity Partnership Future Liquidation Term		8 years	8 years